Sewall Wright
Sewall Green Wright ForMemRS (
December 21,
1889 â€"
March 3,
1988) was an American
geneticist known for his influential work on
evolutionary theory.
Sewall Wright was born in
Melrose,
Massachusetts to Philip Green and Elizabeth Quincy Sewall Wright. He was the youngest of three gifted brothers, the aeronautical engineer
Theodore Paul Wright and the political scientist
Quincy Wright. From an early age Wright had a love and talent for mathematics and biology. Wright attended Galesburg High School, where he graduated in
1906 to enroll in
Lombard College, where his father taught a number of subjects, to study
mathematics. He was influenced greatly by Professor
Wilhelmine Entemann Key, one of the first women to receive a
Ph.D. in
biology. Wright received his Ph.D. from
Harvard University, where he worked with the pioneering mammalian geneticist William Ernest Castle investigating the inheritance of coat colors in mammals. He worked for the U.S. Department of Agriculture until
1925, when he joined the Department of Zoology at the
University of Chicago. He remained there until his retirement in 1955, when he moved to the
University of Wisconsin, Madison. He received many honors in his long career, including the National Medal of Science, the Balzan Prize, and the Darwin Medal of the Royal Society. He was a member of the
National Academy of Science and a Foreign Member of the
Royal Society.
Wright married Louise Lane Williams (
1895-
1975) in 1921, with whom he had three children: Richard, Robert, and Elizabeth.
His papers on
inbreeding,
mating systems, and
genetic drift make him a principal founder of theoretical
population genetics, along with
R. A. Fisher and
J. B. S. Haldane. Their theoreticalwork is the origin of the
modern evolutionary synthesis or
neodarwinian synthesis. Wright was the inventor of the
inbreeding coefficient, a standard tool in
population genetics. He was the chief developer of the mathematical theory of
genetic drift, which is sometimes known as the Sewall Wright effect, cumulative
stochastic changes in gene frequencies that arise from random births, deaths, and Mendelian segregations in
reproduction. Wright was convinced that the interaction of
genetic drift and the other evolutionary forces was important in the process of adaptation. He described the relationship between
genotype or
phenotype and
fitness as
fitness surfaces or
fitness landscapes. On these landscapes fitness was the height, plotted against horizontal axes representing the
allele frequencies or the average
phenotypes of the population.
Natural selection would lead to a population climbing the nearest peak, while
genetic drift would cause random wandering.
Wright's explanation for
stasis was that organisms come to occupy
adaptive peaks. In order to evolve to an other, higher peak, the species would first have to pass through a valley of maladaptive intermediate stages. This could happen by genetic drift if the population is small enough. If a species was divided into small populations, some could find higher peaks. If the there was some gene flow between the populations, these adaptations could spread to the rest of the species. This was Wright's
shifting balance theory of evolution.There has been much skepticism among evolutionary biologists as to whether these rather delicate conditions hold often in natural populations. Wright had a long standing and bitter debate about this with
R. A. Fisher, who felt that most populations in nature were too large for these effects of
genetic drift to be important.
Wright strongly influenced
Jay Lush, who was the most influential figure in introducing
quantitative genetics into animal and plant breeding. Wright's statistical method of
path analysis, which he invented in 1921 and which was one of the first methods using a
graphical model, is still widely used in
social science. He was a hugely influential reviewer of manuscripts, as one of the most frequent reviewers for
Genetics. Such was his reputation that he was often credited with reviews that he did not write.
He did major work on the genetics of
guinea pigs, and many of his students became influential in the development of mammalian genetics. He appreciated as early as 1917 that genes acted by controlling
enzymes.
Wright received
National Medal of Science in
1966.
Wright was one of the few geneticists of his time to venture into
philosophy. He found a union of concept in
Charles Hartshorne, who became a lifelong friend and philosophical collaborator. Wright believed that the birth of the consciousness was not due to a mysterious property of increasing complexity, but rather an inherent property, therefore implying these properties were in the most elementary particles.
Wright and Fisher were the key figures in the
neodarwinian synthesis that broughtgenetics and evolution together. Their work was essential to the contributions of
Dobzhansky,
Mayr,
Simpson,
Julian Huxley, and
Stebbins. The neodarwiniansynthesis was the most important development in evolutionary biology after
Darwin.Wright also had a major effect on the development of mammalian genetics and biochemical genetics.
* Crow, J. F. (1988)
"Sewall Wright (1889-1988)" Genetics 119 (1): 1-4.
* Crow, J. F. and W. F. Dove. (1987)
"Sewall Wright and physiological genetics" Genetics 115 (1): 1-2.
* Ghiselin, M. T. (1997)
Metaphysics and the Origin of Species. NY: SUNY Press.
* Hill W. G. (1996)
"Sewall Wright's 'Systems of Mating'" Genetics 143 (4): 1499-506.
*Provine, W. (1986)
Sewall Wright and Evolutionary Biology. Chicago, IL: University of Chicago Press.
* Wright, S. (1932)
"The roles of mutation, inbreeding, crossbreeding and selection in evolution" Proc. 6th Int. Cong. Genet. 1: 356â€"366.
*
Sewall Wright: Darwin's Successorâ€"Evolutionary Theorist by Edric Lescouflair and James F. Crow
